It depends on the dose. Low dose exposures can allow cells to survive and this could happen. In the treatment with radiation the cancer is treated to levels that are designed to kill the cells and therefore mutation to more aggression is not likely. There are many resistance cancers however and it is more likely the cancer is already aggressive.

In brief:
Yes

In the way you asked the question it can.

It depends on the dose. Low dose exposures can allow cells to survive and this could happen. In the treatment with radiation the cancer is treated to levels that are designed to kill the cells and therefore mutation to more aggression is not likely. There are many resistance cancers however and it is more likely the cancer is already aggressive.
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